KORG OASYS 88 keyboard, no screen, no lights, no any functions

Keyboard turns on at boot up fan starts  but the dis[lay shows an icon of a computer screen disconnected from a computer tower, then screen goes black  none of the function are available and none of the LED lights on the controls light up.
any idea what could be causing that? what to look for? I have visually inspected the capacitors and checked for any loose cable connection and they all seem fine at first glance.